CHICAGO (Reuters) - A tiny fruit fly -- without any input from the
outside world -- will spontaneously change directions, researchers said
on Monday in a finding that just may rescue the notion that free will
not only exists but is a basic function of the brain.

"Neuroscientists have been claiming free will doesn't exist," said
Bjorn Brembs, a neurobiologist of the Free University Berlin in Germany
who led the study.

The claim is based on work in the 1980s by neuroscientist Benjamin
Libet of University of California San Francisco, who discovered that
even before a person made a conscious decision to move, the brain had
already started the process of movement.

Neuroscientists say this so-called "readiness potential" suggests
that the brain simply responds to outside stimuli, and consciousness is
just the brain's way of rationalizing actions the brain has already
determined to take.

"There are many prominent people who claim the main function of the
brain is to compute input to output," Brembs said in a telephone
interview.

COMPLEX ROBOTS

But what if there was no input, Brembs wondered.

He and colleagues devised an experiment with fruit flies in which they were deprived of all external stimuli.

Animals, and particularly insects, are often seen as complex robots,
responding only to external stimuli, said Brembs, whose work appears in
the Public Library of Science journal PLoS One.

The researchers placed a single fruit fly in a pure white chamber --
devoid of visual cues. The fly was fixed in place and its attempts to
turn were recorded. Researchers repeated their experiment on many flies
and analyzed the data using a series of complex mathematical models.

What they found was surprising.

Lacking external input, Brembs said he had expected a pattern of
entirely random movement or noise -- akin to static on a radio that is
tuned between stations. Instead, the flies showed a pattern of flight
that was generated spontaneously by the brain and could not have been
random.

"The decision for the fly to turn left or turn right, which it
changes all the time, has to come from the design of the brain," Brembs
said.

Brembs said the finding reveals a mechanism that could form the biological basis of free will.

"I don't think we've found consciousness in the fruit fly," he said.
"It's like one of the first building blocks, without which you can't go
on."

George Sugihara, a mathematical biologist at the Scripps Institution
of Oceanography at the University of California San Diego who helped
with the data analysis, said the pattern of variability shown by the
fly's choices revealed a non-linear signature -- something typical of
many biological processes.

"We show free will 'can' exist, but we do not 'prove' it does," Sugihara said.

"Our results eliminate two alternative explanations of this
spontaneous turning behavior that would run counter to free will,
namely randomness and pure determinism," he said in an e-mail.

He said the results address the middle ground between simple
determinism -- the brain as an input-output machine -- and utterly
random behavior.

"We speculate that if free will exists, it is in this middle ground," he said.

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